api
board
physics engine + graphics
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touchdevelop api
board
o
sprite-based
o
objects have speed, gravity,
friction (physics engine)
o
game loop (timer event)
o
touch events on sprites
☁ http://www.touchdevelop.com/Documents/gameboard.pdf
touchdevelop api
examples
o
Missile defence
☁ http://touchdevelop.com/ecvs
o
BreakIt! (written by a user)
☁ http://touchdevelop.com/xkmz
o
… (many more games written by users)
touchdevelop api
coordinates and units
(0,0)
positions are based on
pixels
o
Windows Phone 7 platform
mandates 640x800 screen
resolution
o
origin (0, 0) is top left corner
o
extent (640,800) is just
outside of bottom right
corner
Y: (up to) 800 pixel
o
X: 640 pixel
(320,400)
(640,800)
touchdevelop api
coordinates and units
o
sprite positions refer to center of sprite
(makes rotation easy)
o
speed measured in pixels/second
o
acceleration measured in pixels/second2
touchdevelop api
board apis
o
Media→create board
Creates a new game board
o
typical use:
action main
◳board := media→create full board
... create sprites ...
◳board→post to wall
event game loop
... move objects around ...
◳board→update on wall
Important! Makes changes visible
touchdevelop api
board apis
o
Board→set background
Sets the background color
o
Board→set background picture
Sets the background picture
o
Board→set background camera
Sets the background camera
touchdevelop api
board apis
o
o
o
o
o
Board→create text
Create a new text sprite.
Board→create rectangle
Create a new rectangle
sprite.
Board→create ellipse
Create a new ellipse sprite.
Board→create picture
Create a new picture sprite.
Board→create sprite set
Create a new collection for
sprites.
o
o
o
o
Board→create boundary
Create walls around the
board at the given
distance.
Board→create obstacle
Create a line obstacle with
elasticity (from sticky to
complete bounce)
Board→create anchor
Create an anchor sprite.
Board→create spring
Create a spring between
sprites
touchdevelop api
demo/exercise: static
layout
(0,0)
X: 640 pixel
var board: Board
action main
◳board→create ellipse(20,20)
◳board→post to wall
run script to see static layout
Y: (up to) 800 pixel
◳board := media→create board(640)
ellipse
+(20,20)
☀ tip: always sketch on paper
touchdevelop api
create ellipse
create ellipse(w, h)
o
w is width of
enclosing rectangle
o
h is height
w
h
touchdevelop api
gravity
o
gravity is property of board
o
Board→set gravity
sets the uniform acceleration vector for objects on the
board to pixels/seconds2
o
sprites are affected when Board→evolve is called
o
typical use:
var p := senses→acceleration quick→scale(1000)
◳board→set gravity(p→x, p→y)
touchdevelop api
demo/exercise:
gravity
(0,0)
X: 640 pixel
var board: Board
action main
◳board→create ellipse(20,20)
◳board→post to wall
Y: (up to) 800 pixel
◳board := media→create board(640)
ellipse
+(20,20)
event game loop
var p := senses→acceleration quick→scale(1000)
tilt phone to change gravity
◳board→set gravity(p→x, p→y)
Important! Moves things around according
◳board→evolve
to speed/gravity/friction/…
◳board→update on wall
Important! Makes changes visible
touchdevelop api
obstacles
o
by default, board is open, has no boundary; objects
moving off the visual part of the board will simply
continue moving away. Use Board→create boundary to
create reflecting walls around the board
o
use Board→create obstacle(x,y,w,h,elasticity) to create
line obstacle with elasticity:
•
1 means the entire impulse is maintained
•
0 means full absorption of the impulse (a sprite will
stick to the wall).
touchdevelop api
demo/exercise:
bounday
(0,0)
X: 640 pixel
var board: Board
action main
◳board→create boundary(0)
◳board→create ellipse(20,20)
◳board→post to wall
Y: (up to) 800 pixel
◳board := media→create board(640)
ellipse
+(20,20)
event game loop
var p := senses→acceleration quick→scale(1000)
◳board→set gravity(p→x, p→y)
◳board→evolve
◳board→update on wall
tilt phone to change gravity
Important! Moves things around according
to speed/gravity/friction/…
Important! Makes changes visible
touchdevelop api
demo/exercise:
obstacle
(0,0)
var board: Board
action main
◳board→create boundary(0)
◳board→create obstacle(100,100,50,50,1)
◳board→create ellipse(20,20)
◳board→post to wall
Y: (up to) 800 pixel
◳board := media→create board(640)
X: 640 pixel
(100,100)
obstacle +(50,50)
ellipse
+(20,20)
event game loop
var p := senses→acceleration quick→scale(1000)
◳board→set gravity(p→x, p→y)
◳board→evolve
◳board→update on wall
tilt phone to change gravity
Important! Moves things around according
to speed/gravity/friction/…
Important! Makes changes visible
touchdevelop api
create obstacle
create obstacle(x, y, w, h,
elasticity)
o
(x, y) is upper left
corner
o
obstacle is a
straight line
o
(w, h) is size of
bounding rectangle
(x, y)
h
w
touchdevelop api
friction
o
without friction, ball doesn’t slow down
o
set friction:
o
o
•
default setting for entire board
•
custom setting for each sprite
“A friction is the fraction of the forward speed that is
experienced as a backwards force.”
•
friction of 0 corresponds to no friction at all
•
friction of 1 means the sprite will not move at all
example: board→set friction(0.01)
touchdevelop api
demo/exercise:
friction
(0,0)
var board: Board
action main
◳board→create boundary(0)
◳board→create obstacle(100,100,50,50,1)
var ball := ◳board→create ellipse(20,20)
ball→set friction(0.05)
Y: (up to) 800 pixel
◳board := media→create board(640)
X: 640 pixel
(100,100)
obstacle +(50,50)
ellipse
+(20,20)
◳board→post to wall
(new code in bold)
touchdevelop api
springs, anchors
o
a spring lets 2 sprites accelerate towards each other
(without friction, those sprites will oscillate indefinitely)
o
an anchor has infinite friction
touchdevelop api
demo/exercise: springs,
anchors
action main
event gameloop()
◳board := media→create full board
◳board→evolve
var sprite := board→create ellipse(20,20)
◳board→update on wall
var anchor := board→create anchor(10,10)
sprite→move(100,0)
◳board→create spring(sprite, anchor, 100)
sprite→set speed y(100)
This code
◳board→post to wall
produces a sprite
that will circle the
center of the board
touchdevelop api
touch input
o
add event handler, for example:
event tap board: board(x, y)
if y > 400 then
phone→vibrate(0.05)
touchdevelop api
sprites
o
sprites are movable objects
o
use to visually represent parts of a game,
such as your space ship, a bullet, a
monster, etc.
o
create new sprites through the board API
o
change its position, speed, etc
touchdevelop api
sprite properties
o
position: x, y
•
o
set x(x), set y(y), set pos(x, y)
speed: speed x, speed y
•
set speed x(x), set speed y(y), set speed(x, y)
o
rotation (angular speed in
degrees/second), friction, width, height,
color, text, elasticity
o
visibility: is visible/hide/show
touchdevelop api
exercises
►add picture sprite
►add text sprite
touchdevelop api
sprite helper
functions
o
s→move(x, y)
same as
s→pos(s→x + x, s→y + y)
o
s→move towards(s’, f)
same as
s→pos(s→x+f(s’→x-s→x)f, s→y+f(s’→y-s→y)f)
o
s→speed towards(s’, f)
puts sprite on a trajectory towards the other sprite
with a speed vector of the given magnitude.
touchdevelop api
sprite overlap
o
Sprite→overlaps with
Do the sprites overlap
o
Sprite→overlap with
Returns the subset of sprites in the given set
that overlap with sprite
touchdevelop api
sprite set
o
Board→create sprite set
Create a new collection for sprites.
o
add and remove sprites from set,
enumerate over sprites in set (“for each”),
test if a sprite is in a given set, etc.
touchdevelop api
examples
o
counter
☁ http://touchdevelop.com/cvby
o
break countdown
☁ http://touchdevelop.com/khida
o
turtle
☁ http://touchdevelop.com/neyh
o
maze
☁ http://touchdevelop.com/oces
o
juggler
☁ http://touchdevelop.com/fvmq
touchdevelop api
homework
►change example, so that it creates…
•
record sound in main, play when ball is near
boundary
•
5 balls with random sizes, colors, frictions
•
3 obstacles with random position/sizes
►build a game with board, accelerometer
• also consider reacting to touch
touchdevelop api